Normally, an uncooled infrared image sensor has concave portions below a diode array forming pixel units, so as to increase its sensitivity. As the substrate temperature varies, temperature corrections are performed on the pixel units. To perform the temperature corrections, reference pixel units having heat sensitive elements formed on the substrate are placed in the vicinities of the pixel units. The I-V characteristics (current-voltage characteristics) of the reference pixel units are utilized to detect variations in the substrate temperature. In this manner, temperature corrections are performed on the pixel units.
However, the reference pixel units have different I-V characteristics from those of the pixel units, because of their structural differences from the pixel units. Therefore, accurate temperature corrections cannot be performed on the pixel units.